Friday, August 16, 2013

GeoMIP Publishes First Results

The Geoengineering Model Intercomparison Project (GeoMIP), an international collaborative project designed to test the robustness of SRM modeling results across multiple climate models, has released results from its first round of simulations. "Experiment G1" focused on a simple scenario in which results from a preindustrial control run were compared to results from a simulated quadrupling of CO2 concentration in the atmosphere; both runs were then compared to results from a geoengineering simulation in which top of atmosphere (TOA) radiative forcing is initially lowered by a maximum 0.1 W/m2 to mimic the effects of SRM. These test parameters were run using twelve different global climate models to determine which results held relatively constant across multiple models, indicating theoretical agreement on the broad consequences of SRM deployment.

The main findings of G1 include:

Geoengineering can return high temperatures under global warming to preindustrial levels, with some regional variation.

Geoengineering can prevent Arctic sea ice loss under global warming.

Precipitation in the tropics declines under geoengineering due to reduced atmospheric convection.

Plant growth increases in a geoengineered world as a result of the CO2 fertilization effect combined with reduced heat stress.

The authors conclude, "For most of the results presented in this study, changes in G1 [geoengineering simulation] relative to piControl [preindustrial control run] are substantially smaller than changes in abrupt4xCO2 [global warming simulation] relative to piControl" (p. 11). While these scenarios are greatly simplified and highly idealized, comparison of modeling results provides first-order quantitative evidence of how a geoengineered world would look relative to a world experiencing significant climate change without SRM.